Automotive steering column assemblies often include translating and/or deformable members that, in the event of a frontal collision, absorb the driver's energy, thus reducing the forces experienced by the driver. To optimize the column assembly's energy absorption performance, column manufacturers have developed two primary methods of allowing the column assembly to translate during a frontal collision. The first method is to allow the column assembly to collapse along the center line of the steering shaft, best shown in FIG. 1. A steering column assembly 10 includes first and second members 12, 14 telescopically engaged with respect to one another. The first and second members 12, 14 support a steering wheel 16. The first and second members 12, 14 telescopically collapse along the longitudinal axis of the column assembly in response to an impacting force 18 acting on the steering column 16. The steering wheel 16 moves from a first position 20 to a second position 20 (shown in phantom) in response to the impacting force 18, traveling a distance 24.
Typically, the steering shaft is at a 18-22 degree angle from horizontal. This has been the industry standard since it is easily packaged and allows for an internally collapsing column structure. Although column assemblies that collapse along the center line of the steering shaft offer certain benefits, there are disadvantages. One of the major disadvantages is that the relative position between the driver's chest and the airbag changes as the column collapses. Another disadvantage is that the collapse resistance of the column assembly is at an angle relative to the driver's input load.
The second method for allowing the column assembly to translate during a frontal collision is to allow the column assembly to horizontally translate, best shown in FIG. 2. A steering column assembly 110 includes first and second members 112, 114. The first and second members 112, 114 are slidably engaged with respect to one another and support a steering wheel 116. In response to an impacting force 118, the first member 112 and steering wheel 116 move relative to the second member 114. The steering wheel 116 moves from a first position 120 to a second position 122, traveling a distance 124. This allows the driver's input load and the column collapse resistance to be aligned. However, the major disadvantage of the horizontally collapsing column assembly is the inability to internally collapse the steering column structure. This means that the vehicle manufacturer must leave space available for the column assembly to translate during collision.